1. Field of the Invention
The invention relates to power laser sources based on a pumped doped fiber whose core is multimode. Usually the fiber receives a beam emitted by a monomode oscillator. The continuous or pulsed beam output by the fiber is therefore an amplified beam, but its power remains limited. The invention is designed to produce compact and efficient fiber sources delivering a high-power beam with good beam quality.
2. Background Art
The production of laser sources delivering power greater than 1 kW has been demonstrated at the present time in several laboratories using diode-pumped Nd:YAG rods.
Two types of architecture result in such performance: single oscillator and xe2x80x9cMOPAxe2x80x9d configuration, consisting of an oscillator, an amplifier and possibly a phase conjugation mirror. The object of the invention is to propose a diode-pumped fiber source architecture of the MOPA type. Continuous power greater than 100 W can be obtained using quasi-monomode fibers. Taking these results into account, we propose to produce sources delivering more than 1 kW of power using multimode fibers, the volume of the gain medium of which is very much greater than that of a monomode fiber.
The invention therefore relates to a pumped fiber laser comprising a monomode laser oscillator transmitting a monomode laser beam to a first end of a doped fiber, characterized in that the doped fiber is multimode and in that it also includes a spatial mode conversion device receiving the beam. To guarantee diffraction-limited beam quality, a mode conversion device is introduced, which consists of a nonlinear medium serving to record a dynamic hologram or possibly a fixed (volume) hologram.